1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.eventbus;
18
19import com.google.common.annotations.Beta;
20
21/**
22 * Wraps an event that was posted, but which had no subscribers and thus could
23 * not be delivered.
24 *
25 * <p>Subscribing a DeadEvent handler is useful for debugging or logging, as it
26 * can detect misconfigurations in a system's event distribution.
27 *
28 * @author Cliff Biffle
29 * @since 10.0
30 */
31@Beta
32public class DeadEvent {
33
34  private final Object source;
35  private final Object event;
36
37  /**
38   * Creates a new DeadEvent.
39   *
40   * @param source  object broadcasting the DeadEvent (generally the
41   *                {@link EventBus}).
42   * @param event   the event that could not be delivered.
43   */
44  public DeadEvent(Object source, Object event) {
45    this.source = source;
46    this.event = event;
47  }
48
49  /**
50   * Returns the object that originated this event (<em>not</em> the object that
51   * originated the wrapped event).  This is generally an {@link EventBus}.
52   *
53   * @return the source of this event.
54   */
55  public Object getSource() {
56    return source;
57  }
58
59  /**
60   * Returns the wrapped, 'dead' event, which the system was unable to deliver
61   * to any registered handler.
62   *
63   * @return the 'dead' event that could not be delivered.
64   */
65  public Object getEvent() {
66    return event;
67  }
68
69}
70